Abstract
BackgroundRice, which serves as a staple food for more than half of the world’s population, is very susceptible to the pathogenic fungus, Magnaporthe oryzae. However, common wild rice (Oryza rufipogon), which is the ancestor of Asian cultivated rice (O. sativa), has significant potential as a genetic source of resistance to M. oryzae. Recent studies have shown that the domestication of rice has altered its relationship to symbiotic arbuscular mycorrhizae. A comparative response of wild and domestic rice inhabited by mycorrhizae to infection by M. oryzae has not been documented.ResultsIn the current study, roots of wild and cultivated rice colonized with the arbuscular mycorrhizal (AM) fungus (AMF) Rhizoglomus intraradices were used to compare the transcriptomic responses of the two species to infection by M. oryzae. Phenotypic analysis indicated that the colonization of wild and cultivated rice with R. intraradices improved the resistance of both genotypes to M. oryzae. Wild AM rice, however, was more resistant to M. oryzae than the cultivated AM rice, as well as nonmycorrhizal roots of wild rice. Transcriptome analysis indicated that the mechanisms regulating the responses of wild and cultivated AM rice to M. oryzae invasion were significantly different. The expression of a greater number of genes was changed in wild AM rice than in cultivated AM rice in response to the pathogen. Both wild and cultivated AM rice exhibited a shared response to M. oryzae which included genes related to the auxin and salicylic acid pathways; all of these play important roles in pathogenesis-related protein synthesis. In wild AM rice, secondary metabolic and biotic stress-related analyses indicated that the jasmonic acid synthesis-related α-linolenic acid pathway, the phenolic and terpenoid pathways, as well as the phenolic and terpenoid syntheses-related mevalonate (MVA) pathway were more affected by the pathogen. Genes related to these pathways were more significantly enriched in wild AM rice than in cultivated AM rice in response to M. oryzae. On the other hand, genes associated with the ‘brassinosteroid biosynthesis’ were more enriched in cultivated AM rice.ConclusionsThe AMF R. intraradices-colonized rice plants exhibited greater resistance to M. oryzae than non-AMF-colonized plants. The findings of the current study demonstrate the potential effects of crop domestication on the benefits received by the host via root colonization with AMF(s), and provide new information on the underlying molecular mechanisms. In addition, results of this study can also help develop guidelines for the applications of AMF(s) when planting rice.
Highlights
Rice, which serves as a staple food for more than half of the world’s population, is very susceptible to the pathogenic fungus, Magnaporthe oryzae
We obtained four treatment groups for this study: R. intraradices-inoculated cultivated rice infected with M. oryzae (Cp + R), R. intraradices-uninoculated cultivated rice infected with M. oryzae (Cp), R. intraradices-inoculated wild rice infected with M. oryzae (Wp + R), R. intraradices-uninoculated wild rice infected with M. oryzae (Wp)
Cp + R, Rhizoglomus intraradices-inoculated cultivated rice infected with Magnaporthe oryzae; Cp, R. intraradices-uninoculated cultivated rice infected with M. oryzae; Wp + R, R. intraradices -inoculated wild rice infected with M. oryzae; Wp, R. intraradices-uninoculated wild rice infected with M. oryzae
Summary
Rice, which serves as a staple food for more than half of the world’s population, is very susceptible to the pathogenic fungus, Magnaporthe oryzae. Zhang et al (1998) identified a new gene in common wild rice involved in bacterial blight resistance, namely the Xa21, which belongs to the R gene group and is originated from the wild rice species Oryza longistaminata (Ni et al 2015). Another example is the R gene Pi54 that was identified in both wild and cultivated rice and shown to play a role in blast disease resistance (Zhang et al 2018). China has protected several conservation areas to maintain the production of wild rice and preserve its genetic diversity for rice breeding efforts, as well as to provide research materials to investigate the responses of wild and cultivated varieties of rice to various abiotic and biotic stresses (Luo et al 2017; Tian et al 2017)
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